Antioxidants are compounds which can delay or inhibit the oxidation of organic molecules by inhibition of the initiation and/or propagation of oxidizing chain reactions, generally free radical reactions. Species associated with free radical oxidation processes include peroxyl radicals (ROO.), superoxide radicals (O2.−) and hydroxyl radicals (.OH). Many natural and synthetic molecules have antioxidant properties and such character has been quantified, collected and published by the United States Department of Agriculture by listing of oxygen radical absorbance capacities (ORAC). Generally, a wide range of spices, fruits, berries and legumes have been identified as having antioxidant properties. Natural antioxidants provide platforms for the quenching of free radicals.
Conventionally employed biologically safe antioxidants include Vitamin C, Carnosine, Glutathione and Resveratrol. Carnosine (β-alanyl-histidine) is a natural dipeptide that is innate to vertebrates and found to act as a pH buffer, ion-chelating agent and in lipid peroxidation in vitro. Such activity for Carnosine spurs interest in peptide structures, because peptides offer a wide variety of structural modification and molecular design possibilities upon which antioxidant molecules of designed properties may be prepared.
Proteins have also been shown to have antioxidative activities against free radical oxidation of lipids and/or fatty acids. Certain peptides having electron donor properties can react with free radicals to terminate the radical chain reaction, although the exact mechanism of action for such antioxidant peptides is not clearly known. Enzymes involved in anti-oxidation reactions (e.g. superoxide dismutase (SOD), catalase, glutathione peroxidase) play an important role in cellular defense against oxidative stresses. However, there are many issues existing for direct application of such natural redox proteins as antioxidants including bioavailability, safety, stability and cost. Some aromatic amino acids and histidine have been reported to play a vital role in peptides having antioxidant properties.
In view of growing demand for antioxidants designed for attractive cost and structure activity performance that may be used in food, cosmetic and other applications, economical antioxidants based on natural product raw material building blocks are sought. Proteins or long chain polypeptides having interesting antioxidant properties are known; however, the cost of producing synthetic peptides are five to twenty times higher than the cost of conventional antioxidants.
Therefore, the present inventors have analyzed the amino acid sequences of selected redox proteins and have identified short active motifs (less than 6 amino acid residues in length) that possess antioxidant activity. A study of antioxidant properties of short polypeptide molecules has identified specific structure activity relationships which have led to the surprising discovery of cost effective short chain polypeptides having antioxidant activity comparable to or better than conventionally known antioxidants such as Vitamin C and Carnosine.
Therefore an object of the present invention is to discover novel short chain polypeptides containing six amino acid residues or less that have high antioxidant activity and are structurally tailored for specific utility. The short chain polypeptides must be biologically safe and ideally at least economically competitive with the conventionally employed antioxidants. In addition, the amino acid content of the short chain polypeptides will not include the sulfur containing amino acids cysteine and methionine, thus avoiding possible odor problems in production and utilization.
A further object of the present invention is to provide a method to protect a composition from oxidation or to impart antioxidant properties to a composition.
An even further objective of the present invention is to provide a method to protect a keratinous material from free radical degradation.